Chapter 6: Radar Transmitters

Example 1,Page No:231

In [1]:
import math

#variable declaration
F     = 9*10**9;               #Reflex Klystron operating frequency in hz
Va    = 300;                #beam voltage in volts
I     = 20;                 #Beam current in mA
n     = 1;                  # for 7/4 mode

#Calculations
#transit time for reflector space = n+3/4

I1        = I*10**-3;                                  #beam current in mA
Prfmax    =(0.3986*I1*Va)/float(n+3/float(4));         #maximum RF power

#result

print'Maximum R-F power is %3.3f'%(Prfmax),'Watts';

Maximum R-F power is 1.367 Watts

Example 2,Page No:231

In [2]:
import math

#variable declaration
Vdc   = 2.5*10**3;         #Beam voltage
Idc   = 25*10**-3;          #beam current in A;
Zo    = 10;                #charecteristic impedance 
F     = 9.5*10**9;          #TWT operating frequency in hz
N     = 40;                #circuit

#Calculations

C     = ((Idc*Zo)/float((4*Vdc)))**(1/float(3));       #gain parameter
Ap     = (-9.54)+(47.3*N*C);                            #Output power gain of twt
w     = 2*math.pi*F;
vdc   = 0.593*10**6*math.sqrt(Vdc);
Be    = w/float(vdc);

#result

print'Gain parameter is %3.3g'%C;
print'Output Power gain is %3.3f'%Ap,' dB';
print'phase constant of electron beam is %e'%Be,' rad/m';

Gain parameter is 0.0292
Output Power gain is 45.782  dB
phase constant of electron beam is 2.013162e+03  rad/m

Example 3,Page No:232

In [3]:
import math

#variable declaration

e   = 1.609*10**-19;                       #charge of electron
me  = 9.109*10**-31;                       #mass of electron in kg
B   = 0.40;                                 #magnetic flux density
b   = 10*10**-2;                           #Radius of vane edge from the centre
a   = 4*10**-2;                           #radius of cathode


#Calculations

Wc  = (e/me)*B;             #cyclotron angular frequency in radians
Vc  = (e/(8*me))*(B**2)*(b**2)*(1-(a/float(b))**2)**2;   #cut-off voltage

#result
print'Cyclotron Angular Frequency is %g'%Wc,'rad';
print'Cut-off voltage is %g'%Vc,'V';
print'Note:Cut-off voltage obtained in textbook is wrongly calculated.Instead of (a/b)**2 ,(a/b) is calculated';

Cyclotron Angular Frequency is 7.06554e+10 rad
Cut-off voltage is 2.49272e+07 V
Note:Cut-off voltage obtained in textbook is wrongly calculated.Instead of (a/b)**2 ,(a/b) is calculated

Example 4,Page No:232

In [2]:
import math

#variable declaration
Va  = 900 ;                  #Accelarating voltage in volts
F   = 3.2*10**9;              #operating frequency
d   = 10**-3;

#Calculations

Ve       = (0.593*10**6)*math.sqrt(Va);             #electron velocity
w        = 2*math.pi*F;
theta    = w*(d/float(Ve));                        #transit angle in radians
Be       = math.sin(theta/float(2))/(theta/float(2));    #Beam Coupling Co-efficient


#result

print'Electron Velocity is %3.3e'%Ve,'m/s';
print'Transit Angle is %g'%theta,'rad';
print'Beam Coupling Co-efficient is %3.3f '%Be; 

Electron Velocity is 1.779e+07 m/s
Transit Angle is 1.1302 rad
Beam Coupling Co-efficient is 0.948

Example 5,Page No:233

In [3]:
import math

#variable declaration
I2  = 28*10**-3 ;            #induced current in amperes
V2  = 850;                   #fundamental component of catcher-gap voltage
Vb  = 900;                  #beam voltage
Ib  = 26*10**-3;            #beam current
Bc  = 0.946;              #beam coupling coefficient of catcher gap

#Calculations

n   = ((Bc*I2*V2)/(2*Ib*Vb))*100;      #efficiency of klystron


#result
print'Efficiency of the klystron is %g'%n;
print'Note:In textbook Bc value is taken as 0.946 in calculation';

Efficiency of the klystron is 48.1085
Note:In textbook Bc value is taken as 0.946 in calculation

Example 6,Page No:233

In [23]:
import math

#variable declaration
Vd   = 2.2*10**5;           #carrier Drift Velocity in m/s
l    = 5*10**-6;          #drift region length

#Calculations

F    = Vd/float((2*l));           #frequency of IMPATT Diode

#result
print'Frequency of IMPATT Diode is %g'%(F/10**9),' Ghz';

Frequency of IMPATT Diode is 22  Ghz

Example 7,Page No:233

In [25]:
import math

#variable declaration
Vd   = 3*10**5;            #Carrier Drift Velocity in m/s
l    = 7*10**-6;           #drift region length

#Calculations

F    = Vd/float(2*l);       #frequency of IMPATT Diode

#result
print'Frequency of IMPATT Diode is %3.2f'%(F/float(10**9)),' Ghz';

Frequency of IMPATT Diode is 21.43  Ghz

Example 8,Page No:233

In [6]:
import math

#variable declaration
Na   = 1.8*10**15;              #Doping Concentration 
J    = 25*10**3;                #current density in A/cm^2
q    = 1.6*10**-19;             #charge of electron

#Calculations

Vaz  = J/float(q*Na);            #Avalanche Zone Velocity

#result
print'Avalanche Zone Velocity of TRAPATT is %g'%(Vaz);
print'Note: wrong calculation done in Textbook';

Avalanche Zone Velocity of TRAPATT is 8.68056e+07
Note: wrong calculation done in Textbook

Example 9,Page No:234

In [7]:
import math

#variable declaration
l  = 12*10**-3;            #gunn diode oscillator length in m
Vd = 2*10**8;               #Drift velocity in gunn diode

#Calculations

F  = Vd/float(l);                #Frequency of Gunn Diode Oscillator

#result
print'Frequency of Gunn Diode Oscillator is %3.3g'%(F/10**9),' Ghz';

Frequency of Gunn Diode Oscillator is 16.7  Ghz

Example 10,Page No:234

In [8]:
import math

#variable declaration

l      = 2.5*10**-6;         #Drift length of gunn diode in m
Vd     = 2*10**8;             #Drift velocity in gun diode
Vgmin   = 3.3*10**3;          #minimum voltage gradient required to start the diode

#Calculations

Vmin  = Vgmin*l;

#result
print'Minimum Voltage required to operate gunn diode is %g'%(Vmin*10**3),' mV';

Minimum Voltage required to operate gunn diode is 8.25  mV
In [ ]: